Biodiversity & Conservation

SS.SMu.ISaMu.Cap

Explanation of sensitivity and recoverability


Physical Factors

Substratum Loss
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Removal of the substratum, perhaps by dredging, would result in the loss of Capitella capitata, and any other species that may be present, and hence the loss of the biotope so intolerance is assessed as high. Recovery is likely to be very high - see additional information below.
Smothering
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As an infaunal burrowing species Capitella capitata will be unaffected by smothering by a 5 cm layer of sediment because the species thrives in, and often creates, thick muds. Therefore, the biotope is not sensitive to the factor. However, smothering by impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect.
Increase in suspended sediment
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As Capitella capitata is a sub-surface deposit feeder, changes in suspended sediment concentration at the benchmark level are unlikely to have any adverse effect. Therefore, the biotope is probably not sensitive to the factor.
Decrease in suspended sediment
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A decrease in suspended sediment concentration may result in reduced food supply, due to less available organic particles and detritus. However, at the level of the benchmark impacts are not likely to be significant and intolerance has been assessed as low. On return to normal conditions recoverability is likely to be very high.
Desiccation
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Due to the infaunal position of the polychaete, adults are protected from desiccation. This biotope may also occur to some extent in the intertidal. However, survival of larvae may be inhibited. Nevertheless, intolerance has been assessed to be low. Recoverability is likely to be very high (see additional information below).
Increase in emergence regime
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Due to the infaunal position of the polychaete, adults are protected from increased emergence. This biotope may also occur to some extent in the intertidal so can tolerate a degree of emergence. However, survival of larvae may be inhibited. Intolerance has been assessed to be intermediate. Recoverability is likely to be very high (see additional information below).
Decrease in emergence regime
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Capitella capitata is generally sublittoral and so the biotope is unlikely to be exposed to a decrease in emergence.
Increase in water flow rate
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There is no information regarding the water flow rates in which the biotope is found. However, it is likely that water flow would be fairly low since, in high flow rates, the nature of the substratum would be coarse sediment particles as the smaller muddy fraction is washed away. Therefore, the biotope is expected to be intolerant of increases in water flow and a rank of high, but with low confidence, is recorded. On return to normal conditions recovery is likely to be rapid - see additional information below.
Decrease in water flow rate
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There is no information regarding the water flow rates in which the biotope is found. However, it is likely that water flow would be fairly low since muddy sediments are more likely to be found in these conditions. A decrease in suspended sediment concentration may result in reduced food supply, due to less available organic particles and detritus. However, intolerance has been assessed as low because any impacts of a decrease in water flow rate are likely to be sub-lethal only. Recoverability is likely to be very high, on return to normal conditions.
Increase in temperature
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Capitella capitata occurs south of the British Isles and will therefore be subject to greater temperatures. The species has also been recorded around hydrothermal vents (Gamenick & Giere, 1997) which suggests that the species complex would be relatively tolerant to an increase in temperature. Effects of combinations of varying salinities and temperature on Capitella capitata were carried out by Redman (1985; summary only). Under experimental regimes, length of life decreased as follows: 59 weeks at mid-temperature and salinity (15°C, 25ppt); 43 weeks at high temperature & high salinity (18°C, 30ppt); 33 weeks at lower temperature & high salinity (12°C, 30ppt); 17 weeks at high temperature & low salinity (18°C, 20ppt). Redman (1985) also found that net reproduction (Ro: the mean number of offspring produced per female at the end of the cohort) decreased as follows: 41.75 control; 36.69 under high salinity, high temperature; 2.19 high temperature, low salinity; 2.16 low temperature, high salinity. Therefore, a combination of changes in temperature and salinity may decrease the viability of the population. Intolerance to increased temperature has been assessed to be low. On return to normal levels, recoverability is likely to be very high (see additional information below).
Decrease in temperature
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Capitella capitata occurs north of the British Isles and will therefore be subject to lower temperatures suggesting that the species complex would be relatively tolerant to a decrease in temperature. Effects of combinations of varying salinities and temperature on Capitella capitata were carried out by Redman (1985). At lower temperature and salinities (12°C, 20ppt) very few individuals survived. Under other experimental regimes, length of life decreased as follows: 59 weeks at mid-temperature and salinity (15°C, 25ppt); 43 weeks at high temperature & high salinity (18°C, 30ppt); 33 weeks at low temperature & high salinity (12°C, 30ppt); 17 weeks at high temperature & low salinity (18°C, 20ppt). Redman (1985) also found that net reproduction (Ro: the mean number of offspring produced per female at the end of the cohort) decreased as follows: 41.75 control; 36.69 under high salinity, high temperature; 2.19 high temperature, low salinity; 2.16 low temperature, high salinity. Therefore a combination of changes in temperature and salinity may decrease the viability of the population. No other information on the affect of low temperatures on Capitella capitata was found however, since the species is found in waters north of Britain intolerance is expected to be low. On return to normal levels, recoverability is likely to be very high (see additional information below).
Increase in turbidity
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The biotope is a faunal assemblage so the light attenuation effects of an increase in turbidity would not significantly affect the community. Nevertheless, primary production by pelagic phytoplankton and microphytobenthos do contribute to benthic communities and so long term increases in turbidity may reduce the overall organic input to the detritus. Reduced food supply may affect growth rates and fecundity of some species in the biotope. However, at the level of the benchmark effects are not likely to be significant and a rank of low intolerance is reported. On return to normal turbidity levels recovery will be very high as food availability returns to normal. The impacts on deposit feeding are addressed under 'suspended sediment' above.
Decrease in turbidity
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The biotope is a faunal assemblage so the light attenuation effects of a decrease in turbidity would not significantly affect the community. Nevertheless, primary production by pelagic phytoplankton and microphytobenthos do contribute to benthic communities and so a long term decrease in turbidity may increase the overall organic input to the detritus. However, since the biotope occurs in organically enriched habitats the impact of changes in primary production is likely to be insignificant and a rank of not sensitive is recorded. Reduced food supply may affect growth rates and fecundity of some species in the biotope. However, at the level of the benchmark effects are not likely to be significant and a rank of low intolerance is reported. On return to normal turbidity levels recovery will be very high as food availability returns to normal. A rank of not sensitive is recorded. The impacts on deposit feeding are addressed under 'suspended sediment' above.
Increase in wave exposure
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The biotope occurs in sheltered locations and is likely to be intolerant of an increase in wave exposure. Increased wave action would re-suspend the sediment increasing oxygenation and maybe changing the nature of the substratum as fine particles are washed away. Capitella capitata thrives in conditions of high nutrients and moderate hypoxia so anything that reduces these factors may allow other species to colonize the area and out-compete it.
Decrease in wave exposure
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The biotope normally occurs in locations that are extremely sheltered from wave action so a further decrease is considered to be not relevant.
Noise
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Capitella capitata may be able to detect vibration, and withdraw into their burrow, reducing the amount of time available for feeding. However, at the benchmark level the species is unlikely to be sensitive to noise and so the biotope is assessed as not sensitive.
Visual Presence
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Capitella capitata may be able to detect shadows, however, at the benchmark level the species is unlikely to be sensitive to visual presence and so the biotope is assessed as not sensitive.
Abrasion & physical disturbance
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The infaunal nature of Capitella capitata may offer some protection from abrasion. Bonsdorff & Pearson (1997) found that sediment disturbance forced the polychaete deeper into the sediment, although the species was able to burrow back through the sediment to the surface again. However, the polychaete burrows close to the sediment surface and has a fragile body that may be easily damaged by the impact of an anchor or mobile fishing gear. Intolerance has been assessed as intermediate. Recoverability is likely to be very high (see additional information below).
Displacement
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Shull (1997) demonstrated that Capitella capitata colonizes areas by bedload transport, among other methods. Therefore, if Capitella capitata is displaced onto suitable substrata it is likely to be able to form a new burrow. However, during this period the species will be exposed to greater risks of predation and so intolerance to displacement has been assessed to be low. Recoverability is likely to be very high.

Chemical Factors

Synthetic compound contamination
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Capitella capitata is an opportunist especially associated with organically enriched and polluted sediments (Warren, 1977; Pearson & Rosenberg, 1978). The species often thrives in polluted conditions so the biotope is not likely to be especially intolerant of the factor. However, Capitella capitata may not be able to tolerate all synthetic chemicals and so an intolerance rank of low is reported.
Heavy metal contamination
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Experimental studies with various species suggests that polychaete worms are quite tolerant to heavy metals (Bryan, 1984). High numbers of Capitella capitata have been recorded in areas containing high metal concentrations (Petrich & Reish, 1979; Ward & Young, 1982; Rygg, 1985; Olsgard, 1999), although abundance of Capitella capitata in Norway has also been noted to have a significant negative correlation between sediment content of Cu and abundance of the species with an obvious reduction in abundance at approximately 900 ppm Cu (Olsgard, 1999). Some impacts on population size and reproduction of Capitella capitata as a result of metal pollution, both in the field and the laboratory, have been observed. Refer to the Capitella capitata species review for full details. However, the species does appear to tolerate high metal concentrations, and so intolerance has been assessed to be low. On return to normal conditions recoverability is likely to be very high.
Hydrocarbon contamination
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Suchanek (1993) reviewed the effects of oil spills on marine invertebrates and concluded that, in general, on soft sediment habitats, infaunal polychaetes, bivalves and amphipods were particularly affected. However, high numbers of Capitella capitata have been recorded in hydrocarbon contaminated sediments (Ward & Young, 1982; Olsgard, 1999; Petrich & Reish, 1979) and colonization of areas defaunated by high hydrocarbon levels may be rapid (Le Moal, 1980). Available information (see the species review for more details) suggests that Capitella capitata is able to withstand relatively high hydrocarbon concentrations and may even take advantage of any available space, caused by mortality of other species. Therefore the biotope has been recorded as not sensitive*.
Radionuclide contamination
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There is insufficient information to make an assessment.
Changes in nutrient levels
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Capitella capitata is an opportunist especially associated with organically enriched and polluted sediments (Warren, 1977; Pearson & Rosenberg, 1978) so an increase in nutrients is likely to be beneficial to the biotope. Holte & Oug (1996) found that during periods of influx of organic material Capitella capitata is capable of explosive population growth, often becoming predominant, under high input levels, to the exclusion of nearly all other species. Only when nutrients are so high that severe hypoxia or complete anoxia occurs does Capitella capitata not survive. Therefore, the benchmark level of increase in nutrients is not likely to have a major impact on the biotope and any that does occur will be beneficial. However, the biotope may be intolerant of a decline in nutrient levels. Capitella capitata is often associated with enriched sediments although it is just as often found in organically poor areas (Eagle & Rees, 1973). However, in these conditions other species are also able to survive and may out-compete Capitella capitata. Thus, as nutrient levels decrease other species may appear and the abundance of Capitella capitata will decrease such that the biotope will be lost. Nevertheless, in terms of the benchmark, the biotope is expected to be not sensitive*.
Increase in salinity
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The biotope occurs in areas of full salinity although will be subject to some variability because of rainfall in the intertidal. There are no reports of the biotope occurring in hypersaline areas such as rockpools where evaporation in the summer causes salinity to increase. Although Capitella capitata may be able to tolerate increased salinity it is unlikely such a change will occur in the field and so the factor is ranked as 'not relevant'.
Decrease in salinity
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Capitella capitata occurs in the seaward portion of estuaries (salinities >18 ppt) and, under corresponding conditions in non-tidal brackish waters (Barnes, 1994), can withstand considerable salinity fluctuations (Leppäkoski, 1975) and showed a positive correlation to decreasing salinity in an estuary in Java, Indonesia (Soemodinoto et al., 1995).Therefore, Capitella capitata has a low intolerance to a decrease in salinity and the biotope is also ranked as low.
Changes in oxygenation
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Diaz & Rosenberg (1995) classify Capitella capitata as a species resistant to 'moderate' hypoxia with oxygen decline to about 0.7mg/l. In laboratory experiments testing hypoxia tolerance at 5-6°C most Capitella capitata survived >24 days at an oxygen concentration of 1.5ml/l (2.1mg/l, Rosenberg, 1972). Bolam & Fernandes (2002) and Shull (1997) noted that Capitella capitata can colonize azoic sediments rapidly in relatively high numbers. Only completely anoxic sediments will be completely azoic. Thus, because of the ability of Capitella capitata to tolerate hypoxic conditions the biotope will have low intolerance to changes in oxygenation at the level of the benchmark.

Biological Factors

Introduction of microbial pathogens/parasites
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No information on diseases affecting Capitella capitata or the biotope was found.
Introduction of non-native species
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No known non-native species compete with Capitella capitata and so the biotope is assessed as not sensitive. However, as several species have become established in British waters there is always the potential for an adverse effect from a non-native species to occur.
Extraction
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Extraction of Capitella capitata is highly unlikely because the species has no commercial value. However, bottom fishing for demersal species may deplete populations in some habitats. The infaunal nature of Capitella capitata may offer some protection from dredging / trawling. Bonsdorff & Pearson (1997) found that sediment disturbance forced the polychaete deeper into the sediment, although the species was able to burrow back through the sediment to the surface again. However, the polychaete burrows close to the sediment surface and has a fragile body that may be easily damaged by the impact of an anchor or mobile fishing gear. Intolerance has been assessed as intermediate. Recovery is likely to be very high because Capitella capitata is iteroparous and is thought to breed all year (see additional information).

Additional information icon Additional information

Recoverability
Capitella capitata has an opportunistic life history and year round breeding. Bolam & Fernandes (2002) and Shull (1997) noted that Capitella capitata can colonize azoic sediments rapidly in relatively high numbers. Shull (1997) also demonstrated that this occurs by larval settlement, bedload transport and by burrowing. For example, after dredging in Canada, rapid colonization of Capitella capitata took place (Wildish & Thomas, 1985). Since Capitella capitata colonization can reach maturity within about 40 days, populations may be established and breeding within 6 months of a new substratum becoming available. Thus, recovery is very high.

This review can be cited as follows:

Hill, J. & Bilewitch, J. 2009. Capitella capitata in enriched sublittoral muddy sediments. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 31/10/2014]. Available from: <http://www.marlin.ac.uk/habitatbenchmarks.php?habitatid=106&code=2004>